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Validation of a DNA-based method for the determination of hazelnut oil in olive oil

Project Code: Q01095

24/10/2008

Campden BRIDooley, J

Increasing consumer demand for premium quality and speciality oils can attract fraudulent substitution of expensive oils with similar cheaper products. The premium price attracted by olive oil makes it a particular target for adulteration with less expensive hazelnut oil. In order to protect consumers from this practice a method is required to ensure the authenticity of olive oil and to allow for enforcement of the Olive Oil Marketing Regulation which controls the marketing standard for the selling of olive oil.
Standard analytical techniques are not able to reliably detect low levels of adulteration of olive oil with hazelnut oil due to their chemical similarity. Therefore the suitability of recently developed DNA-based methods needs to be investigated to establish a robust method to detect olive oil adulteration.
The optimised assay validated in this study was shown to offer a high level of sensitivity and accuracy for the detection of hazelnut adulteration of olive oil at levels between 2 and 20%. During blind testing using a range of authentic samples from different commercial mills, 96% of samples were correctly classified with respect to the presence or absence of unrefined hazelnut oil. This study has allowed the validation of a DNA-based method for the accurate detection of unrefined hazelnut oil in olive oil, which can in turn be considered better than or at least comparable to current stand methods for detecting the adulteration of virgin olive oil with unrefined hazelnut oil. A validated SOP for this method is available for use.